Expansion anchors are inserted into a pre-drilled hole and then their shanks are normally tightened using a torque wrench. It has proven necessary to employ a torque wrench because the user cannot see whether the expansion anchor inserted into the hole has expanded, that is to say, whether it has been installed properly. During this process, problems occur if the expansion is insufficient, meaning that the anchor does not have adequate holding force in the substrate, and also if the expansion is excessive, since this might cause fatigue of the expansion anchor. Accordingly, manufacturers of expansion anchors indicate the appropriate tightening torque at which the torque wrench should be set for the installation procedure.